Initial stages of SiGe epitaxy on Si(001) studied by scanning tunneling microscopy

Abstract

We have studied the initial stages of strained SiGe alloy growth on the Si(001)-(2 × 1) surface by scanning tunneling microscopy. The Si0.36Ge0.64 alloy was grown on the silicon substrate at various coverages (0.13-3.6 ML) and at different temperatures (~ 310-470°C). The growth was one dimensional, preferring the direction perpendicular to the underlying silicon dimer rows at low coverages and low temperatures. Anti-phase boundaries were observed to lead multi-layer growth. Strong interaction between the overlayer and the substrate was found to buckle the substrate as well as SiGe dimers. Different growth mechanisms, island formation and step flow, were identified at low and high substrate temperatures. (2 X n) ordering of the strained overlayer was only observed at an intermediate growth temperature (~ 390°C).

Hydrogen desorption in SiGe films: A diffusion limited process

“…This is supported by the fact that in pure Si and Ge, dimerization in the surface occurs. [11][12][13][14] The dimers can be found in three possible states of hydrogen occupancy: clean ͑''unoccupied dimers''͒, characterized by a interaction between the atoms forming the dimer, singly occupied ͑where hydrogen adsorption breaks the double bond resulting in a Si-H or Ge-H bond and an unpaired dangling bond͒, and doubleoccupied. ͑2͒ Hydrogen desorption occurs by pre-pairing of two hydrogen atoms in a single dimer.…”